Circuit breaker



April 21, 1942 H. CLAYTON 2,280,231

CIRCUIT BREAKER Filed Oct. 5, 1939 2 Sheets-Sheet l vfl r 7 Z kINVENTOR. ffarold f2. Clgyi'of; B ,W-

ATTORNEYS. 3

April 21, 1942. H. H. CLAYTON CIRCUIT BREAKER Filed Oct. '5, 1939 2Sheets-Sheet 2 a Raf m VJ T MM 2 H, 9 P v w W Fm w 0 0 0 7 Patented Apr.21, 1942 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Harold H. Clayton,Logansport, Ind., assignor to R-B-M Manufacturing Company, Logansport,11111., a corporation of Indiana Application October 5, 1939, Serial No.297,995

Claims.

tain length of time.

The object and general nature of the present invention is the provisionof a circuit breaker in which a thermally responsive member is operativeto interrupt the circuit under abnormal conditions but is held by anelectromagnet, also disposed in the circuit, against opening the circuituntil the thermal element exerts sufllcient force to overcome the pullof the electromagnet, thereby securing a circuit interruption at a ratethat is sufllcient to reduce or eliminate arcing. A further feature ofthis invention is the provision of a circuit breaker which includes anelectromagnet operating in opposition to the thermal element so as tohold the contacts closed in a firm and positive manner, therebypreventing any tendency to openthe circuit momentarily under conditionswhere the circuit breaker is subjected to jars and vibration.

These and other objects and advantages of the present invention will beapparent to those skilled in the art after a consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which:

Figure l is a longitudinal section taken through a circuit breaker inwhich the principles of the present invention have been incorporated;

Figure 2 is a top view of the circuit breaker shown in Figure l, withthe perforated cover removed;

Figure 3 is a section taken along the line 3-2 of Figure 1;

Figure 4 is a longitudinal vertical sectional view of a modified form ofcircuit breaker forming another embodiment of my invention;

Figure 5 is a top plan view, partly in section, of the modified circuitbreaker of Figure 4; and

Figure 6 is a side elevational view of modified thermal element mountingmeans.

Referring now more particularly to Figures 1 and 2, the referencenumerall indicates a base upon which the parts of the circuit'breakerare carried, the ends of the base I being turned downwardly and bentoutwardly, as indicated at 2 and 3, respectively, forming attaching earsby which the circuit breaker may be mounted in place on any suitablesupport. The base plate I carries two insulating strips I and 5 on theinner and outer portions, respectively, of the base I. U-shaped core I,formed of iron or the like, is supported on the base I by any suitablemeans, such as a rivet 8 which passes through the central portion of theU-shaped core member and through an opening in the base I and insulatorplates 4 and 5, the mounting being such that the core I is out ofelectrical contact with the base I. One side 9 of the member 1 isextended laterally, as at II), to form a support for a thermallyresponsive member I2 which is riveted. as at I3, or otherwise secured tothe end It and extends across the upper portion 01' the other side II ofthe Ushaped core member. The central part of the core member I isextended, as at It, to form a terminal.

A coil I'I surrounds the core section I5, the latter forming the coreproper for the coil I1, and one end of the latter, as indicated at I9,is fixed in electrical contact by a lug or tongue to a bracket 2|fastened in insulated relation to the base plate I by any suitablemeans, such as rivets 23, The other end of the coil I1 is flxed in anysuitable manner to a plate 26.which extends laterally outwardly of thebase I and has an end 21 formed as a terminal and lying alongside theterminal end I6 which, as best shown in Figure 2, is formed on orcarried by the central portion of the U-shaped core member 9.

The bracket 2i includes a base 3|, an upstanding portion 32, and ahorizontal portion 33 disposed generally above the terminal plate 26, asbest shown in Figure 3. A stationary contact 35 is fixed in any suitablemanner to the bracket section 33. As best shown in Figures 1 and 2, the

. latter is formed with a rearward extension which possesses someresilience, due to the notched out construction, as indicated at 34 inFigure 2.

Preferably, the tongue 20 is punched from the vertical portion 22 of thebracket and then crimped against the coil end I9. The coil Il may beformed of relatively heavy gage wire having an enamel or similarinsulating covering, which is, of course, removed at the point where theends I9 and 25 are connected to the bracket 2i and terminal plate 26,respectively.

The thermally responsive member I2 is preferably in the form of abimetal strip secured at one end by the rivet l3 to the core lug III,the other end of the strip I2 carrying a movable contact 31. An armatureformed of suitable material is carried by the strip I2 in axialalignment above the core section 05. The armature preferably has ears Mwhich are bent over and secured to the bimetal strip 62, as best shownin Figure 2. The ears 2 and 3 serve to support a cover having aplurality of perforations 46 formed therein, and if desired the cover 45may be riveted to the ears 2 and 3 so as to make a compact tamper-proofunit.

The operation of the circuit breaker of the present invention issubstantially as follows:

The circuit breaker unit is, of course, designed to have a propercapacity for use with the system in which it is to be placed. Where thecircuit breaker is adapted for automotive use, it may be inserted in themain line from the battery or generator to the various lamp, ignition,signalling circuits and the like so that normally current flows from-thebattery or generator through the circuit breaker unit to the variousoperating units. that under normal conditions it exerts a spring forceholding the contacts 35 and 31 in engagement. minal 21 through the coilH to the bracket 2|, and from thence to the contacts 35 and 31 on thebimetal strip l2, the arm section 9 and the terminal l6. The coil I1 iswound so that a normal current flow exerts an electromagnetic forceagainst the armature 46, pulling down on the bimetal strip I2 andholding the contacts 35 and 31 firmly and positively in engagement. Theheat due to a normal flow of current through the bimetal strip 12 is notsufilcient to cause the strip to warp upwardly against the force of theelectromagnet |1 holding the same down, but in the event of an overload,as for example a short circuit, there is sufficient flow of currentthrough the bimetal strip I! to cause the same to get sufflciently hotenough to warp upwardly and overcome the pull of the electromagnet l1,thus separating the contacts 35 and 31 and interrupting the circuit.Before this occurs, however, the bimetal strip |2 will be stressed anappreciable amount, otherwise it would not be possible to overcome thepull of the electromagnet l1. Hence, the moment the contacts 35 and 31are separated and the electromagnet deenergized, the bimetal strip l2quickly separates the contacts 35 and 31 so that little or no arcingoccurs between the contacts. This is an important feature of myinvention.

When the contacts 35 and 31 are separated, as described, the abnormalflow of current is interrupted. and since no current is then flowingthrough the bimetal strip |2, the same cools due to the circulation ofair through the openings 46 in the cover 45. and gradually warpsdownwardly until the contacts 35 and 31 come into engagement. The momentthis occurs the current flow through the unit is resumed, and thesimultaneous energization of the electromagnet l1 exerts a force throughthe armature 40 against the bimetal strip l2 immediately pulling thecontacts 35 and 31 into relatively high pressure engagement so thatsubsequent jars and vibration cannot produce a momentary separation ofthe contacts 35 and 31. If the unit was constructed so that vibrationsproduce momentary separations at the contacts 35 and 31, the resultingarcing at these points might soon cause them to freeze or stick,disabling the unit.

With a view of providing a circuit breaker compensated for change inambient temperatures, the circuit breaker designated generally at 50 inFigures 4 and 5 of the drawings illustrates one The bimetal strip I2 isconstructed so The normal current flows from the tera stamped member 52.

embodiment of my invention. The circuit breaker 56 comprises a base 5ion which is mounted Insulating members 53 and 64 are provided on thesupport member 52, and a frame 55 is carried on the top insulator 53.Terminals 55 and 51 are provided on the base 5| which turn up under thebottom insulator 54, as shown. Terminal posts 58 and 59 are provided-for the terminals 56 and 51 respectively. A core 60 of an electromagnetis mounted on the center of the frame 55 and a reduced end passesthrough an aperture in the frame 55, insulating members 53 and 54, andsupport member 52, as shown. The core 68 is spun over at its lower endas shown at 6| to securely hold it in place. An insulating washer 62insulates the core 60 from the support 52. A paper insulating tube 63 isdisposed over the top of the core 68 to insulate it from the coil orsolenoid 64 of the electromagnet. An eyelet 65 is provided through theinsulating members 53 and 54 and the support 52 through which oneterminal of the solenoid 64 may be connected to the terminal 51. Theeyelet 65 is insulated from the support 52 by the insulating washer 66.The terminal of the solenoid 64 is secured to the eyelet 65 by a depositof solder as shown at 61.

A contact support 10 carrying a contact 1| is mounted on the rightupstanding arm of the frame 55 by a rivet 12 between insulating members13 and 14. The support 10 is insulated from the rivet 12 by theinsulating washer 15. A leaf spring 16 is secured to the left upstandingarm of the frame 55 by means of a rivet 11. A bracket 18 is mounted onthe leaf spring 16 as shown, which carries a bimetallic thermally andmagnetically responsive element 80. vThe bimetallic element carries asecond contact 8| which is adapted to cooperate with the contact 1|carried by the contact support 10. In order to compensate the bimetallicelement 80 for changes in ambient temperature, a bimetallic compensatingmember 82 is mounted therewith as shown, while a holding screw 83secures the bimetallic elements 80 and 82 to the bracket 18. In order toadjust the force with which the contact 8| is biased against the contact1|, an adjusting screw 84 is provided in the lower end of the bracket 18which is adapted to bear against the center of the leaf spring 16. Whenthe proper adjustment has been obtained by turning the adjusting screw84 in or out as required, it may be held in place by a deposit of solder85. In order to house the circuit breaker 50, a cover 86 is disposedthereover which may be secured to the support 52 and the base 5| byrivets 81 as shown.

In operation, the terminal posts 58 and 59 are connected in the circuitto be protected. The current flows through the solenoid 0r coil 64,thereby energizing the electromagnet and causing the bimetallic element80 to be attracted to the core 60. The second terminal of the solenoid64 is connected to the contact support member 10 by the deposit ofsolder as shown at 90 in Figure 5 of the drawings. The energizingcurrent flows through the contact support member 18 through the closedcontacts 1| and 8|, through the bimetallic element 80, bracket 18, leafspring 16, frame 55, lower reduced portion oi the core 60, and throughthe terminal strip 56 to the terminal post 58. The bimetallic element 80is adapted to bias the contact 8| against the contact 1| under normalcurrent flow. If the current flow should exceed the predetermined safeload, the FR loss will heat the bimetallic element 80 so as to cause itto turn away or upwardlyand pull the contact II from the contact II. Theinstantthat the contacts 8| and Ii are separated, the circuit will bebroken, thereby deenergizing the electromagnet energized by the solenoid64, allowing the contact 8| to snap sharply from the contact ll. Whenthe temperature of the bimetallic element 80 falls, it will again biasthe contact 8| against the contact H, thereby closing the circuitthrough the solenoid i4 and causing the bimetallic element 88 to beagain attracted to the core 60. Instead of having the current passdirectly through the bimetallic element 80, it might be passed through aheater element surrounding the bimetallic element 80.

It will be observed that not only is the bimetallic element" responsiveto the heat due to the current, but also to any other rise intemperature. Accordingly, in order to make it substantially responsiveonly to the current heat, the compensating bimetallic member 82 ismounted therewith. The bimetallic compensating element 82 turns in theopposite direction of the bimetallic element 88 with the same change intemperature. In this manner changes in ambient temperature affecting thebimetallic element 80 are compensated for. The bimetallic compensatingelement 82 has a thin coating of oxide which tends to electricallyinsulate this element from the actuating element 80. Furthermore. thiscompensating element 82 is of high resistance material and is of shortthick formation so that no appreciable current flow or resultant heatingeffect occurs within the compensating element.

Referring now to Figure 6 of the drawings, a modified form of mountingarrangement for the bimetallic element 80 is designated generally at 85.Instead of providing a separate compensating bimetallic element as 82 inFigures 4 and of the drawings, the bracket 18, or the leaf spring 16, orboth of these parts, may be of bimetallic metal. When either the bracket18 or the leaf spring I6, or both of these parts, are composed ofbimetallic metal, they are so disposed that their action opposes that ofthe bimetallic element 8!! with the same change in ambient temperature.In this manner the biasing force with which the contact 8| is heldagainst the contact ll depends substantially only on the current heatingeffect on the bimetallic element 80. The

bracket I8 and the leaf spring 18, whether made of bimetallic metal ornot, are of low resistance material so as to reduce the heating effectof the current passing through these parts.

Since certain further changes may be made in t the foregoingconstructions, and different embodiments of the invention may be madewithout departing from the scope thereof, it is intended rying one ofsaid contacts. an electromagnet adapted to attract said bimetallicelement, and a compensating bimetallic member operatively connected withsaid bimetallic element and adapted to compensate for the effect ofchange in ambient temperature on said bimetallic element, the solenoidof said electromagnet and said bimetallic element being in seriescircuit relationship when said contacts are closed, under normal currentflow through the circuit breaker biasing said contacts together, andsaid contacts being separated with snap action when excessive currentflows causing said bimetallic element to flex so as to separate thecontacts and thereby to deenergize said electromagnet and allow thecontacts to spring apart. v

2. A circuit breaker comprising, in combination, a pair of contacts, abimetallic element carrying one of said contacts, electrical heatingmeans for said bimetallic element, an electromagnet adapted to attractsaid bimetallic element, and a compensating bimetallic memberoperatively connected with said bimetallic element and acting oppositelythereto so as to compensate for the effect of change in ambienttemperature on said bimetallic element, the solenoid of saidelectromagnet and said electrical heating means being in series circuitrelationship when said contacts are closed, under normal current flowthrough the circuit breaker said bimetallic elementand saidelectromagnet biasing saidcontacts together, and said contacts beingseparated with snap action when excessive current flows causing saidbimetallic element to flex so as to separate the contacts and thereby todeenergize said electromagnet and allow the contacts to spring apart.

3. A circuit breaker comprising, in combination, a frame, a firstcontact supported from said frame and electrically insulated therefrom,a bracket supported by said frame, a first bimetallic element supportedby said bracket, a second contact carried by said first bimetallicelement adapted to cooperate with said first contact, a secondbimetallic element mounted with said first bimetallic element and actingin opp sition thereto so as to compensate said first bimetallic elementfor changes in ambient temperature, and

an electromagnet for attracting said first -bi 40' metallic element, thesolenoid of said electromagnet and said first bimetallic element beingin series circuit relationship when said contacts are closed, undernormal current flow through the circuit breaker said first bimetallicelement and said electromagnet biasing said contacts together, and saidcontacts being separated with snap action when excessive current fiowscausing sa d first bimetallic element to flex so as to separate thecontacts and thereby to deenergize said electromagnet and allow thecontacts to spring apart.

4. A circuit breaker comprising, in combination. a frame, a firstcontact supported from said frame and electrically insulated therefrom,a bimetallic bracket supported by said frame, a bimetallic elementsupported by said bimetallic bracket, said bimetallic bracket adapted tocompensate said bimetallic element for changes in ambient temperature, asecond contact carried by said bimetallic element adapted to cooperatewith said first contact, and an electromagnet adapted to attract saidbimetallic element, the solenoid of said electromagnet and saidbimetallic element being in series circuit relationship when saidcontacts are closed, under normal current flow through the circuitbreaker said bimetallic element and said electromagnet biasing saidcontacts together, and said contacts being separated with snap actionwhen excessive current fiows causing said bimetallic element to flex soas to separate the contacts and thereby to deenergize said electromagnetand allow the contacts to spring apart.

5. A circuit breaker comprising, in combina- 1d m t m 1 and saidelectromagnet tion, a frame, a first contact supported from said frameand electrically insulated therefrom, a bimetallic spring supported bysaid frame, a breaket supported bysaid spring, a bimetallic elementsupported by said bracket, said bimetallic spring adapted to compensatesaid bimetallic element for changes in ambient temperature, a secondcontact carried by said bimetallic element adapted to cooperate withsaid first contact, and an electromagnet adapted to attract saidbimetallic element, the solenoid of said electromagnet and saidbimetallic element being in series circuit relationship when saidcontacts are closed, under normal current flow through the circuitbreaker said bimetallic element and said electromagnet biasing saidcontacts together, and said contacts being separated with snap actionwhen excessive current flows causing said bimetallic element to flex soas to separate the contacts and thereby to deenergize said electromagnetand allow the contacts to spring apart.

6. A circuit breaker comprising, in combination, a frame, a firstcontact supported from said frame and electrically insulated therefrom,a leaf spring supported from said frame, a bracket supported by saidspring, a first bimetallic element supported by said bracket, a secondcontact carried by said first bimetallic element adapted to cooperatewith said first contact, a second bimetallic element mounted with saidfirst bimetallic element and adapted to compensate it for changes inambient temperature, an adjusting screw carried by said bracket forregulating the force with which said leaf spring biases said contactstogether, and an electromagnet for attracting said first bimetallicelement, the solenoid of said electromagnet and said first bimetallicelement being in series circuit relationship when when said contacts areclosed, under normal current flow through the circuit breaker said firstbimetallic element and said electromagnet biasing said contactstogether, and said contacts being separated with snap action whenexcessive current flows causing said first bimetallic element to flex soas to separate the contacts and thereby todeenergize said electromagnetand allow the contacts to spring apart.

'7. In a protective circuit breaker, the combination of a stationarycontact and a movable contact normally remaining in engagement, a

thermally responsive element operative to move said movable contact outof enagement with said stationary contact when the temperature of saidthermostatic element is raised substantially to a predetermined point,compensating means responding to ambient temperature and cooperatingwith said thermally responsive element, and a stationary electromagnetacting magnetically on said thermally responsive element and tending tohold said contacts in engagement, the resistance of said thermallyresponsive element being such that the heat generated from within saidthermall responsive element by a predetermined overload current flowtherethrough stresses said element with sufficient force to overcome themagnetic attraction of said electromagnet and thereby separates saidcontacts with a snap motion.

8. In a protective circuitbreaker, the combination of a U-shapedstationary frame member, thermally responsive means including abimetallic operator and a bimetallic compensator carried on one arm ofsaid frame member, a stationary electromagnet carried by said framemember and acting magnetically on said bimetallic operator, a stationarycontact, and a movable contact actuated by said bimetallic operator andnormally remaining in engagement with said stationary contact, saidelectromagnet tend ing to hold said contacts in engagement, saidthermally responsive means operating to move said movable contact out ofengagement with said stationary contact when the temperature of saidthermally responsive means is raised substantially to a predeterminedpoint, said thermally responsive means, said electromagnet and saidcontacts being connected in series, whereby heat generated by apredetermined overload current flow stresses said thermally responsivemeans with sufficient force to overcome the magnetic attraction of saidelectromagnet and thereby separate said contacts with a snap motion.

9. In a protective circuit breaker, the combination of a U-shapedstationary frame member, thermally responsive means including abimetallic element carried on one arm of said frame member, a stationaryelectromagnet carried by said frame member and acting magneticallyonsaid bimetallic element, a stationary contact, a movable contactactuated by said bimetallic element and normally remaining in engagementwith said stationary contact, said electromagnet tending to hold saidcontacts in engagement, said bimetallic element operating to move saidmovable contact out of engagement with said stationary contact when thtemperature of said element is raised substantially to a predeterminedpoint, said thermally responsive means, said electromagnet and saidcontacts being connected in series, whereby heat generated by apredetermined overload current flow stresses said bimetallic device withsufficient force to overcome the magnetic attraction of saidelectromagnet and thereby separate said contacts with a snap motion anda compensating element coacting with said bimetallic element tocompensate for the effect of change in ambient temperature on saidbimetallic element.

10. In a protective circuit breaker for series connection with a loadcircuit adapted normally to remain in closed circuit position in theload circuit and to move to open circuit position only upon an overloadcurrent fiow in said load circuit, the combination of a U-shapedstationary frame member composed of magnetic material, a stationarycontact carried on one arm of said frame member, a bimetallic strip,mounting means including a leaf spring for mounting said bimetallicstrip on the other arm of said frame member, a movable contact carriedby said metallic strip normally remaining in engagement with saidstationary contact, said bimetallic strip flexing to move said movablecontact out of engagement with said stationary contact when thetemperature of said bimetallic strip is raised substantially to apredetermined point, and a stationary electromagnet comprising amagnetic core stationarily secured to said U-shaped frame member betweenthe arms thereof and acting magnetically on said bimetallic striptending to hold said contacts in engagement, said contacts, saidbimetallic strip and said electomagnet being connected in series and theresistance of said bimetallic strip being such that the heat generatedfrom within said bimetallic strip by a predetermined overload currentflow therethrough stresses said strip with sufficient force to overcomethe magnetic attrac- I 2,280,281 -tion of said electromagnet and therebyseparates said contacts with a snap motion.

11. In a protective circuit breaker for series connection in a loadcircuit adapted normally to remain in closed circuit position in theload circuit and to move to open circuit position only upon an overloadcurrent flow in said load circuit, the combination of a U-shapedstationary frame member composed of magnetic material, a stationarycontact carried on one arm of said frame member, a leaf spring carriedby the other arm of said frame member, a mounting bracket carried bysaid leaf spring, a bimetallic strip mounted on said bracket, a movablecontact carried by said bimetallic strip normally remaining inengagementwith said stationary contact, said bimetallic strip flexing tomove said movable contact out of engagement with said stationary contactwhen I the temperature of said bimetallic strip is raised substantiallyto a predetermined point, a stationary electromagnet comprising amagnetic core stationarily secured to said U-shaped frame member betweenthe arms thereof and acting magnetically on said bimetallic striptending to hold said contacts in engagement, said contacts, saidbimetallic strip and said electromagnet being connected in series, andthe resistance of said bimetallic strip being such that the heatgenerated from within said bimetallic strip by a predetermined overloadcurrent flow therethrough stresses said strip with suflicient force toover come the magnetic attraction of said electro magnet and therebyseparates said contacts with a snap motion, and a compensatingbimetallic member carried by one arm of said u-shaped an electromagnetacting in opposition to said thermally responsive means, saidelectromagnet being electrically connected to have its circuit openedwhen said contacts separate, and compensating means for compensating thedevice for ambient temperature.

13 In a circuit breaking device, the combination of a pair of contactsadapted to control a circult, thermally responsive means operative toimpart movement to one of said contacts, said thermally' responsivemeans being electrically connected in series with said contacts wherebycurrent flow through said contacts also passes through said thermallyresponsive means, an

electromagnet opposing separation of said contacts, said electromagnetbeing electrically connected to have its circuit opened when saidcontacts separate, and compensating means disposed substantially out ofthepath of the current flow through the device for compensating saidthermally responsive means for ambient temperatures.

14. In a circuit breaking device of class described, the combination ofa stationary contact and a cooperating movable contact adapt-ed tocontrol a circuit, a bimetallic actuating element operative to move saidmovable contact, said himetallic actuating element having a circuit paththerethrough so as to be heated by the current flow through the device,an electromagnet opposing separation of said contacts, the energizationof said electromagnet being controlled by said contacts, and abimetallic compensating element substantialy isolated from the circuitpath through said bimetallic actuating element but mechanicallycooperating with said bimetallic actuating element to compensate thedevice for changes in ambient temperature.

15. In a circuit breaking device of the class described, thecombination'of a stationary contact and a cooperating movable contactadapted to control a circuit, a main bimetallic element carrying saidmovable contact at'one end, mounting means establishing a movable hingemounting for the other end of said main bimetallic element, magneticmeans acting on an intermediate portion of said main bimetallic elementand tending to retain said contacts in engagement, and a compensatingbimetallic element carried by the movable hinge mounting of said mainbimetallic element and compensating the device for changes in ambienttemperature.

HAROLD H. CLAYTON.

